The Epidemiology And Molecular Biology Study Of An Outbreak Of Aseptic Meningitis Caused By Echo Virus 30

Purpose: To investigate about the aseptic meningitis outbreak caused by enterovirus in Zhangqiu Jinan in 2003. From the direction of field-Epidemiology, we preliminarily describe the distribution of disease in order to study the epidemical risk factors linked with the outbreak; And for etiology . depending on the established methods of virus isolation, neutralization test and fast RT-PCR technology, we must make it clear that what on earth the pathogen is; then to confirm the genotype of Shandong isolated strains by checking and analyzing VP1 genetic sequence of ECHO30.Materials and methods: All information came from the documents obtained from investigation about the outbreak and individual survey. 43 stool specimens, 24 acute-phase and 14 convalescent-phase sera were collected respectively. Virus isolation, serotype identification and neutralization test were according to the 《Manual for the Virological Investigation of Poliomyelitis》 .Total RNA were extracted from 19 strains isolates by Trizol and reverse-transcribed as cDNA, subjected to polymerase chain reaction, then, sequenced. Specimens of seroepidemiology were collected by multi-stage sampling , n=(ts)~2/δ=38, 7 age groups ,20 cases in each group in every county, total 397 and 248 serum samples were in case group and control group respectively. To test the neutralizing antibody titer against the isolated strains by neutralization test. All data was analyzed by SPSS12.0.Results: There was an aseptic meningitis outbreak in Zhangqiu county, Jinnan, the peak incidence occurred in July and August, with 1.81%o of the attack rate, total 1743 cases were reported from June to September in 2003. Most of the cases were children less than 15 years, The age-specific peak incidence occurred from 5 to 9 years old. Male were much more than female, sex ratio is 1.57 : 1. Attack rate indicated that geographical-specific distribution resembled as an open fan in shape from Mingshui to east direction. Fever (94.56% ), headache (95.96% ), vomiting (82.87%) were the predominant clinical manifestations. All patients recovered completely and no death. The aseptic meningitis outbreak caused by a single ECHO30 was identified by conventional method. Physical-chemical characteristic experiments showed these ECHO30 isolated strains with "D" feature, and virulence enhanced. The result of complete VP1 genetic sequence and homology analysis suggested that there were nucleotides divergence between isolated strains and the prototype strains Bastianni. Phylogenetic tree based on complete VP1 sequence showed the Zhangqiu strains formed a single branch together with SD03-TA strains and Zhejiang strains as a new gene group 6. The technology of RT-PCR and genetic sequence could accelerate the course of pathogen diagnose, which would benefit patients and society. Results of seroepidemiology showed that an outbreak of aseptic meningitis associated with ECHO30 surely existed in Zhangqiu, and the type-specific virus-neutralizing antibody titers of case-group was higher than that of control-group, geometric mean titer (GMT) were 1 : 53.08 and 1 ' 32.45 respectively, the antibody titer distribution of case-group concentrate from 1 .' 64 ~ 1 '. 256, the positive rate of antibody reached 90.93%, it showed that population immunity was enhanced after an epidemic of infectious disease. Epidemic risk factors of the outbreak were attributed to the following three reasons: firstly, ECHO30 strains apparently did not endemic in Zhangqiu before; secondly, nucleotides divergence between isolated strains and the prototype strains Bastianni resulted in "D" feature of virulence enhanced; finally, the physical geography circumstances and diet custom advantaged the outbreak in that area. cpntir* mpninaitic r.ntVirpaV vuaa rnncpri hv a variant nfwhich apparently did not circulate before in Zhangqiu area in 2003. Henceforth, we should establish effective surveillance system to prevent and control the diseases caused by non-polio enteroviruse.